A first-of-its-kind flu shot using mRNA technology has been approved for adults 50 years of age and older by the Food and Drug Administration (FDA). 

Moderna’s mFlusiva is the company’s fourth mRNA-based product approved in the United States, according to a Moderna press release. The vaccine has full approval for people 50 to 64 years of age. For those over 65, the FDA granted “accelerated approval,” which is temporary: Full approval depends on the long-term safety and real-world effectiveness of the vaccine in this age group.

Earlier this year, it seemed that the vaccine would never make it to market. The FDA refused to review Moderna’s application, saying that instead of comparing mFlusiva to the standard-dose seasonal influenza vaccine, the company should instead have used the high-dose vaccine, which is recommended for adults who are 65 and older. Also, Health Secretary Robert F. Kennedy Jr. has questioned the safety of mRNA, which is the same technology used to produce the COVID-19 vaccines.

However, a week later, the FDA reversed its decision and agreed to review Moderna’s application after outcry from infectious disease experts and warnings that outright refusal to review the application could cause a chilling effect that would deter investments in new pharmaceuticals and dampen innovation. 

“This approval also reflects the ongoing potential of our mRNA platform to help address important public health challenges through continued scientific innovation,” said Moderna CEO Stéphane Bancel, MBA.

Moderna said it expects to have doses of mFlusiva available for this respiratory virus season. Moderna’s other mRNA vaccines are for respiratory syncytial virus and COVID-19, including a COVID shot approved for infants as young as 6 months. 

mRNA may be key to a more efficacious flu vaccine 

The FDA’s approval of mFlusiva is welcome news, as it provides another vaccine option to help protect people from a virus that sends hundreds of thousands of Americans to the hospital each year, said Ronald G. Nahass, MD, president of the Infectious Diseases Society of America.

“Demonstrating the success of mRNA for influenza opens the door to broader applications, accelerating our ability to create safe and targeted vaccines for a wider range of preventable diseases,” Nahass said in a statement.

Flu vaccines made with traditional methods require months of lead time. But the flu mutates quickly, making it difficult to create a vaccine that’s a good match for the virus. Though the flu vaccine reduces the severity of illness, it’s typically less than 50% effective at preventing infection in a given year.

Manufacturing mRNA vaccines is faster, so theoretically the flu vaccine can be updated as the virus changes, giving hope that mFlusiva will prevent more severe illness and death. The Centers for Disease Control and Prevention estimates that 45,000 people died of influenza during the 2024-25 flu season.